Fan



- usually referred to as Patented May-14, 194s IT-so I ims- PATENT orsica p lbs I v .Boland L. Lincoln, Devan-Mala, 'assignor to.

flrderarhlioston,

B. F. Sturtevant Company,

.Application September 28,1944, serial No. 556,191 a This invention. 'relatestoparatus for controlling the volume of air moved by centrifugal fans. i

As discussed in'the Hagen U. S.,Patent No. 1,846,863, it is desirable to operate a. centrifugal fan at constant speed and to vary the volume of air moved by the fan by varying the spin velocity of the air entering the fan, in the direc tion of rotation of the fan blades. j The air leaving the blades of axial flow fans, ropeller fans, spinsin the direction of rotation of the fan blades, and this invention utilizesthis effect by placing a propeller I fan in the inlet of a'centrifugal fan and varying the spin from the propeller fan for varying the 1 air volume moved by the centrifugal fan. The propeller fan used izone which has the character-. istics of moving a elatively small volume of air axially but adding; considerablespin to the air drawn through it by the centrifugal fan.

An object of the invention is to vary the volume of ir moved by a centrifugal fan by varying the spin in the air from a propeller fan in the inlet thereof. e v e The invention will now be described with reference to the drawing, of which: I

Fig. 1 is a sectional view of a combined centrifugal and propeller fan embodying this inven tion, the speed of the propeller fan being adiustable, and

Fig. 2 is a sectional view of a combined cen- 1 Claim. (01. zen-114) methods of and apwhich varies motor 'speedby varying the resistance in themotor field circuit.

In the operation of the embodiment of the in-' vention illustrated by Fig. 1, the centrifugal fan wheel is operated at constant speed. when the maximum air volume is desired, the propeller fan I! is not. rotated or is rotated at such a low speed that it has substantially no effect on the air.

reduced air volumes are desired, the speed When of the propellerfan -8 is increased. The spin given the air increasescontormably with the increase in speed and the volume of air delivered by the fan decreases conformably with the increase in spin. 1

The embodiment of the invention illustrated by Fig. 2 is similar to that of Fig. 1 except that the propeller fan It is mounted in the axially extending, cylindrical inlet passage and is attached to the hub 28 which is keyed to rotate with, while slidably movable axially on, the axially extending inner portion 28 of'th fan pulley 21 which is iournalle'd for rotation on the shaft 12. The

' trifugal and propeller fan embodying this inven tion, the axial position of the propeller fan in the inlet of the centrifugal-fan being adjustable.

The fan illustrated by Fig. 1 is a centrifugal fan similar to that disclosed by the H. F. Hagen U. 5. Patent No. 2,117,418 and'diflers therefrom.

only bythe inclusion in its inlet of a belt driven propeller fan and the provision of a variable speed motor for rotating the propeller fan;

Referring now to Fig. 1, the casing it which is the usual scroll shaped casing has mounted therein the centrifugal fan wheel ii rotatably mounted on the shaft 12. The wheel II has the blades ll attached to the side plate ll and the back plate I. The shaft 12 isadapted to be rotated by an external motor which is not illustrated. The curved inlet plate I! attached at H to the casing l0 provides a converging inlet lever has the pins 3| which slide in the slot 31 in the. hub 28, and is pivoted at- 32 to a wall of the inlet passage, and is connected through the pivoted links 33 and it to the control levee.-

The spin imparted to the air entering the centrifugal fan wheel is varied by moving the lever 35 along the calibrated segment 36. Movement of the lever results in the axial displacement of the propeller fan with reference to the centrifugal fan wheel. As the propeller fan is moved closer to the centrifugal fan wheel, the spin effect is increased, and as the propeller fan is moved further from the centrifugal fan wheel, the spin effect is decreased. This because the spin begins to straighten out as soon as it leaves the propeller fan. Thus as the control arm 35 is adjusted to decrease the distance between the propeller fan and the centrifugal fan wheel, the spin in the air entering the centrifugal fan whee increases,

and the volume of air delivered by th mg, usal fan decreases conformabl What is claimed 1 A fan assembly comprising in combination, a

fan wheel, means forming a cylindrical air inlet passage extending axially to the inlet of said wheel, a shaft for rotating said wheel, a hub rotatably mounted around said shaft in said pas sage, propeller blades attached to said hub, means for rotating said hub for imparting a spin by said blades to the air entering the inlet of said wheel; and means for slidably' positioning said hub along said shaft for varying the distance of said blades from said wheel for varying. the degree of spin in the air entering said wheel.

ROLAND 1.. 'Lmcomi. I 

